Process of making a photographic mask of high isoelectric point gelatin



Nov. 15, 1949 D. DEAN ET AL PROCESS OF MAKING A PHOTOGRAPHIC MASK OF HIGH ISOELECTRIG POINT GELATIN Filed Feb. 28, 1948 DAVID DEAN ROBERT C. HOUCK INI-"ENTORS BY Q. LAZM Patented Nov. 15 1949 PROCESS OF A PHOT()(Sr-R'APHIC' -MASK OF HIGH IS'OELECTRIC :PQINT 'GELA'TIN D'avid -'Dean and Robert Houck, Rochester, N. -Y., :assignors to Eastman Kodak Company, Rochesten-N. Y., a corporation'of New Jersey Application "February 28, 1948, Serial No.. 1'2-, 017

1 'Thi's inventionrelates to color photography and r'a'articularlyto a method'of masking or color correcticn for use incolor photography. It is well known that 'the'light absorptions of the dyes-or coloring material used in athree-color subtractive photography are incorrect certain spectral regions. It is customary to use'a mask when printing from a 'tl iree-eol'or photographic image in order to overcome --the-ffiects 0f the undesired "spectral absorptions The usual method of com- 'pensating for the-'deficiencies of th'e'dyes orcolor materials in such processes consists in the use -o'f-a negative color-correction mask in contact 'with the transparency when making the printing exposure as described, for example, in Evans' TJ. S. Patent2303;653;Hanson u s. 2;294,98'1 and-elsewhere.

Aconvenient metho'd of masking a three-color photographic' transparency is described in Evans secured to the color transparency. A further object is to provide a masking emulsion which may be dyed while in contact with the usual multi-layer transparency without dyeing the multi-layer material. Other objects will appear from the following description of our invention.

These objects are accomplished according to our inventionby using "for the masking emulsion a gelatinhaving a higher isoelectric point than the gelatin used in the-color "transparency. This permits the masking image-to be dyed Without dyeing the gelatin-of the color transparency, as

described ;more fully hereinafter.

In the accompanying drawing, :the :figure :isa flow-sheet showing the film insectional views at various stages in our process.

Our method is intended for use with all types of photographic transparencies, for example, a multi-color image produced by the process of and Hanson' U.:S=. Paterit 2,371,746-,-granted"March 20 Mannes and Godowsky V Patent 2, 52 71 20; 1945. According -'to the -meth0d described in that patent,=a-sensiti-ve emulsion isplaced incontact "-Withthecolor transparency and-is exposed through-the transparency with light of suitable color to effect :the desired i correction. The *film thus 5 exposed is then removed and a processed to a relief :image which is dyed gray-and which may be retouiched-iwith colored dyes to secure the desired 'correction. 'The rel-ief imageis-appliedwith its support side to the e'mulsion o'f the color transparency :and the :combined structure may thenbeiexp'osed' to obtain-a corrected-color print. Thism'ethod has the disadvantage-thatthe masking film must be' remoVed from the color transparency I after the masking exposure 7 order --'to pro'cess the masking image. If the-relief masking image were placed in a dye 'bath 'while in contact withthe color transparency,- the dye would contaminate the color transparency. -When' the masking film-"is removed from the color transparency, it .must "be re-registered with the'color transparency in orderto-make the printing'exposure.

It is therefore'an object of the present invention to provide a masking method-which will secure the advantages oftbereliefmaSk of Evans and Hanson 'U. S; Patent 23711746 without the attendant-disa'dvantages; 'A furtherobject of "our invention 'is to provide a masking method in which themasking emulsion may be permanently granted August 19, =I94'1. A multi-co1or-transparency produced as described in that patent consists, for example, of a support having-thereon superposed emulsionlayers which are processed to obtain-cyan, 'magenta and yenowuye images respectively. The dyes use'd irr suchtransparencies are deficient with respect to spectral .absorption as mentioned above and ar-maskin-g correction is desirable when printing from the imagein the transparency. The ggelatin ordinarily used in such films is a lime-process gelatin whichv has an isoelectric point at approximately PH 5.

The masking film which WGgDI'QPOSG to;usexhas an emulsion made from gelatinhavingza higher isoelectricppoint than thatlof the gelatin used in the color transparency emulsions. It is ..con-- venient to use for the masking emulsion an acid process gelatin having an isoelectricpointlin the region of pI-I'T' and upwards. .Such1.gelatin=:and a method of producing it are described inrSh eppard and Hudson U. S. Patent 2,101,877, granted December "14, 1937. It is well known" that such gelatinmay be dyed with acid dyes, whereas the ordinary lime-process gelatin having an; isoelectricpo'int in the neighborhood of {pH F5 would not "be substantially dyed, providedthata: suitabiepn is hosenfor the dye-bath- ("Ihe' Sorption 5b of Soldb-le Dyes 'byGeiat'm, Sheppard, Houck 3 and Dittmar, Journal of Physical Chemistry, vol. 46, 1942, page 158).

According to our process a gelatin emulsion made from high isoelectric point gelatin such as an acid-process gelatin is used as the masking material. This emulsion may be coated on the thin support of a dry-stripping material or may be of some other structure which permits its application to the color transparency to be masked. The support of the masking emulsion is cemented to the emulsion side of the multi-color transparency in any suitable way as by the use of a gelatin cement or other cement. This leaves the emulsion of the masking material outermost or away from the multi-color emulsions. An alternative method of applying the masking emulsion would be to cement the emulsion side of the masking film, as a stripping film, to the support side of the transparency. .The supportof the stripping film would then be removed. It will generally be desirable to use a panchromatic masking emulsion so that any of various desired corrections may be secured. Generally, it is desirable to expose the masking emulsion with red monochromatic light through the color transparency.

After exposure of the masking material through the color transparency, the entire film was placed in a developer of the following composition for minutes at 68 F.

Grams Monomethyl p-aminophenol sulfate 2.5 Sodium sulfite (dessicated) 30 I-Iydroquinone 2.5 Sodium metaborate lO Potassium bromide 0.5

Water to 1 liter The sandwich was then washed for five minutes and treated for four minutes in the following solution in order to tan the gelatin in the region of the developed image.

R- Formula (without acid) Stock Solution A:

Water cc 500 Ammonium bichromate grams Water to make liter 1.0 Stock Solution B:

Water liter 1.0

Sodium chloride grams Add 1 part of B to 1 part of A.

After a one-minute rinse, the material was washed in water at 120 F. until clear, and the silver removed by bleaching in a ferricyanide bath of the following composition for two minutes:

Grams Potassium ferricyanide 80' Potassium bromide Water to 1 liter followed by treatment in a hypo solution of the following composition for 10 minutes:

Grams Sodium thiosulfate 320 Sodium sulfite (dessicated) 10 Water to 1 liter The relief image thus formed was dyed by placing the entire sandwich in a dye solution at pH 5.5 for approximately 4 minutes to produce the de-- sired dye density. Suitable acid dyes which may be used depending upon the correction desired are Anthraquinone Blue (C. I. 1089) and Orange II (C. I. 151) (J. S. Chem. Ind. 1887, page 5 9l).

4 Both of these dyes are acid dyes and dye the gelatin of the masking image easily, without appreciably dyeing the gelatin of the color transparency.

Other suitable dyes, together with their Color Index numbers, are:

Color Index No.

The gelatin which we used for the masking emulsion had an isoelectric point at about 8.8 while the isoelectric point of the gelatin of the color transparency was about 4.8. The usual lime-process gelatin has an isoelectric point in of Physical Chemistry, referred to above.

ordinarily has an isoelectric point less sharply defined but in the region of pI-I 7 and upwards. It is not necessary to our process that the isoelectric points be this far removed from each other. For example, differential dyeing may be secured with an acid gelatin having an isoelectric point at a pH of 6 or 7 when the pH of the isoelectric point of the gelatin of the color transparency is approximately 4.7 to 5.0. The pH of the dye bath is also a critical factor in obtaining difierential dyeing as pointed out in the publication by Sheppard, Houck and Dittmar in Journal The pH of the dye bath must be above the pH of the isoelectric point of the gelatin of the color trans. parency and should be below the pH of the isoelectric point of the gelatin of the masking emulsion.

According to a. modification of our invention, the masking emulsion of high isoelectric point gelatin is a stripping emulsion on a temporary support, and may be laminated either to the emulsion side or to the support side of the multicolor transparency to be masked. The support .of the stripping film is removed before or after exposure of the masking emulsion, leaving the emulsion attached to the multi-color transparency. If the masking emulsion is applied to the support side of the multi-color transparency, it may be removed after printing the masked transparency, by swabbing with water.

Our invention will now be described by reference to the accompanying drawing. As shown in the first stage of the drawing, a color transparency consisting of a support ill having thereon emulsion layers ll, l2 and i3 containing cyan, magenta and yellow images, respectively, in low isoelectric point gelatin is in contact with the masking film consisting of a transparent support I4 having thereon a sensitive silver halide emulsion I5 made from high isoelectric point gelatin. As stated above, the masking film may be laminated to the emulsion I3 in any convenient way.

After exposure of the masking emulsion through the color transparency, the masking emulsion is developed, hardened, washed 01f to form a relief and dyed as described above. This leaves a dyed relief gelatin mask It as shown in the second stage of the drawing.

According to a further modification of our invention, if the color transparency is made from gelatin having a high isoelectric point, such as acid process gelatin ithan isoelectric point at pH 6 or above, the masking emulsion may be of low isoelectric point gelatin, for example, at a pH of 4.7 to 5. In this case, a basic dye or mixture of dyes, such as Chrysoidine (Color Index, No. 21) and Methyl violet (Color Index, No. 680) may be used to dye the gelatin of the mask. Basic dyes dye gelatin only at a pH above that of its isoelectric point. The dye bath would be used at a pH between the pHs 0f the isoelectric points of the two types of gelatin in the transparency and mask, to dye only the mask.

The term gelatin as used herein, includes 7 ordinary lime-process gelatin, acid-process gelatin as defined above, gelatin derivatives and deaminated gelatin such as the gelatin described in Sheppard and Hudson U. S, patent application Serial No. 631,216, filed November 27, 1945, now abandoned.

It will be understood that the examples and modifications included herein are illustrative only and that the invention is to be taken as limited only by the scope of the appended claim-s.

We claim:

1. A process of making a color-corrected color print which comprises laminating to a multicolor transparency having multi-colored subtractive dye images in emulsions of gelatin having an isoelectric point of about pH 4.7 to 5.0, a masking film having a single layer silver halide emulsion in gelatin having an isoelectric point of pH greater than that of the gelatin of the transparency, exposing said masking emulsion through the color transparency and, While the masking film is in contact with the multi-color transparency, dyeing the masking emulsion with an acid dye at a pH above that of the isoelectric point of the gelatin of the color transparency and below that of the isoelectric point of the gelatin of the masking emulsion.

2. The process of claim 1 in which the gelatin of the emulsion of the masking film is an acidprocess gelatin.

3. The process of claim 1 in which the gelatin of the emulsion of the masking film has an isoelectric point in the region of pH 7 and upwards.

DAVID DEAN. ROBERT C. HOUCK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,266,435 Nadeau et a1. Dec. 16, 1941 2,362,593 Staehle Nov. 14, 1944 2,367,551 Yule Jan. 16, 1945 2,371,746 Evans et al Mar. 20, 1945 OTHER REFERENCES Journal of Physical Chemistry, vol. 46, 1942, pp. 158- 76. 

